How reliable was the satellite data analysis done by British company Inmarsat to locate Malaysia Airlines flight MH370?
More importantly, why did the analysis take so long?
Associate Professor Randy Chue from the Nanyang Technological University's School of Mechanical and Aerospace Engineering told The New Paper that it was the first time such an analysis was done and Inmarsat "sent the results to other engineers and peers - who are not disclosed - who came back with the same conclusions."
This information was relayed to Malaysian government officials by March 12, but the Malaysian government did not publicly acknowledge it until March 15, according to the Wall Street Journal.
However, Prof Chue said the government did not disclose the information until the other consulting experts "came to the same conclusion" as Inmarsat.
According to UK daily The Telegraph, Inmarsat's role in the search for MH370 began immediately after the aircraft disappeared.
Prof Chue said that though the plane's communications addressing and reporting system was switched off, one of Inmarsat's satellites continued to pick up a series of hourly "pings" from a terminal on the plane.
By studying these pings, Inmarsat was able to establish that MH370 continued to fly for at least five hours after it left Malaysian airspace.
The analysis also showed that the plane ended up along one of two "corridors", one arcing north and the other south, he said.
These pings from the satellite, along with assumptions about the plane's route, helped to narrow down the search area.
How Inmarsat plotted final route of plane:
Even though the entire airplane's communications system had stopped, UK's Inmarsat managed to detect pings, which are transmitted hourly automatically from the plane's terminal.
Engineers then looked at the "Doppler Effect", which is the change in frequency due to the movement of the satellite.
From there, they concluded that the plane flew for at least five hours along one of the two corridors.
Further analysis of a more detailed model of the Doppler Effect and comparisons of similar trajectory of other aircraft on similar route established that MH370 most likely took the southern route.
They then narrowed down the search area to only three per cent of the corridor.
What is the Doppler Effect?
The Doppler Effect describes how a wave changes frequency relative to the movement of an observer (satellite).
Imagine a police siren getting louder as it comes towards you and getting more faint as it goes away from you.
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